XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
Movavi Photo Manager - Focus on the memories, forget about managing photos
IrfanView - IrfanView ... one of the most popular viewers worldwide.
Photos on macOS - Photos keeps your images organized and accessible. Rediscover favorite shots with Memories. Access them on your devices with iCloud Photos.
Seer - A Windows Quick Look Tool in Qt.
Eye of Gnome (eog) - Simple image viewer for the GNOME desktop.